The present invention relates generally to an implantable medical electrical lead; and more particularly, relates to a lead having an occlusion balloon at the distal end of the lead that may be used for obtaining a fluoroscopic image of the vascular system while a lead is located in a vessel, and for temporarily anchoring the lead at a desired implant site.
Implantable medical electrical stimulation and/or sensing leads are well known in the fields of cardiac stimulation and monitoring, including cardiac pacing and cardioversion/defibrillation. In the field of cardiac stimulation and monitoring, endocardial leads are placed through a transvenous route to locate, one or more sensing and/or stimulation electrodes along or at the distal end of the lead in a desired location within a heart chamber or interconnecting vasculature. In order to achieve reliable sensing of the cardiac electrogram and/or to apply stimulation that effectively paces or cardioverts the heart chamber, it is necessary to accurately position the electrode surface against the endocardium or within the myocardium at the desired site and fix it during an acute post-operative phase until fibrous tissue growth occurs.
The pacemaker or defibrillator implantable pulse generator (IPG) or the monitor is typically coupled to the heart through one or more of such endocardial leads. The proximal end of such a lead is typically formed with a connector which connects to a terminal of the IPG or monitor. The lead body typically comprises one or more insulated conductive wires surrounded by an insulating outer sleeve. Each conductive wire couples a proximal lead connector element with a distal stimulation and/or sensing electrode. An endocardial cardiac lead having a single stimulation and/or sensing electrode at the lead distal end and a single conductive wire is referred to as a unipolar lead. An endocardial cardiac lead having two or more stimulation and/or sensing electrodes at the lead distal end and two or more conductive wires is referred to as a bipolar lead or a multi-polar lead, respectively.
In order to implant an endocardial lead within a heart chamber, a transvenous approach is utilized wherein the lead is inserted into and passed through the subclavian, jugular, or cephalic vein and through the superior vena cava into the right atrium or ventricle. An active or passive fixation mechanism is incorporated into the distal end of the endocardial lead and deployed to maintain the distal end elect in contact with the endocardium position.
More recently, endocardial pacing and cardioversion/defibrillation leads have been developed that are adapted to be advanced into the coronary sinus and coronary veins branching there from in order to locate the distal electrode(s) adjacent to the left ventricle or the left atrium. The distal end of such coronary sinus leads is advanced through the superior vena cava, the right atrium, the valve of the coronary sinus, the coronary sinus, and may further be advanced into a coronary vein communicating with the coronary sinus, such as the great vein. Typically, coronary sinus leads do not employ any fixation mechanism and instead rely on the close confinement within these vessels to maintain each electrode at a desired site.
Routing an endocardial lead along a desired path to implant the electrode or electrodes in a desired implantation site, either in a chamber of the heart or in the selected cardiac vein or coronary artery, can be difficult. This is particularly true for steering leads through the coronary sinus and into a branching vein on the left myocardium. Anomalies in the vascular anatomy and the number of branch veins associated with the anatomy make locating the desired path challenging.
Several common approaches have been developed to place electrodes within the left side of the heart. According to one approach, a guide catheter is steered into the desired location in the vasculature. A lead is then fed through the inner lumen of the catheter such that the lead electrode(s) are positioned at predetermined locations. The guide catheter may then be withdrawn. This type of approach is described in commonly assigned U.S. Pat. Nos. 6,006,137, 5,246,014, and 5,851,226 incorporated herein by reference. The described systems employ highly flexible, catheters surrounding the lead body.
When using a guide catheter, it may be difficult to locate a desired implant site within the torturous curves of the venous system. This is particularly true if the implant site is located within the coronary sinus or one of the branch veins. To aid in locating the desired implant site, radiopaque dye may be injected into the venous anatomy so that the coronary veins are visible using a fluoroscopic device. This procedure, sometimes referred to as a xe2x80x9cvenogramxe2x80x9d, allows the surgeon to determine the appropriate path to be followed when performing the implant.
Venograms may be performed using a catheter having an inflatable balloon located on the distal tip. After the distal tip of the catheter has been located within the appropriate position within the vasculature, such as in the coronary sinus, the balloon is inflated to temporarily occlude the backflow of blood into the vein. The radiopaque dye may then be injected through a catheter lumen located distal to the balloon so that the dye is retained within the vessels long enough to obtain the venogram. The balloon may then be deflated to allow blood flow to resume. The surgeon may then use the map of the cardiac vasculature to steer a pacing or defibrillation electrode to the implant site.
Such a system is described in U.S. Pat. No. 6,122,522 to Tockman which describes a guide catheter having a balloon on a distal tip. After a venogram is taken, the balloon is deflated to allow a guidewire to be passed through a central lumen of the catheter and into the appropriate venous pathway. The guide catheter is then withdrawn from the venous system and a pacing lead is advanced over the guidewire for placement at the implant site.
One disadvantage of the system described in the xe2x80x2522 patent is that once the catheter is withdrawn, another venogram can not readily be obtained. Thus, if the surgeon encounters difficulty in placing the lead, the guidewire and lead must be withdrawn, and the catheter re-inserted within the vasculature. This is time consuming and increases the risk of venous perforation.
What is needed, therefore, is a system and method that allows a venogram to be obtained while a lead is still in place within the vasculature.